Ontology is a term that is often found in standards and papers on modeling and enterprise integration, but the concept is often not clearly understood. .
As it is used in enterprise integration, an ontology refers to the specification of the conceptualization by which components of the enterprise share information. An ontological commitment is "an agreement to use a vocabulary (i.e., ask queries and make assertions) in a way that is consistent (but not complete) with respect to the theory specified by an ontology. We build agents that commit to ontologies. We design ontologies so we can share knowledge with and among these agents."
This definition is given in the article:
T. R. Gruber. A translation approach to portable ontologies. Knowledge Acquisition, 5(2):199-220, 1993. Available on line.